No, the total amount of withholding is in Box 2 of the W-2. That would include any additional amount that he indicated on his Form W-4 that he wanted withheld. If enough taxes weren't withheld, he may want to consider filing a new Form W-4.
The IRS has a withholding calculator: IRS Withholding Calculator
And TurboTax can help you determine your withholding and prepare a new W-4 to give to your employer. See the following FAQ:
https://ttlc.intuit.com/replies/3301783
